I don't get it

I recently wrote a new women’s thriller. I thought of this really great twist for the ending, and then kind of worked my way backwards.

The first person who read the book thought the twist was pretty cool. But then my mother read it.

“I don’t understand the ending,” she said.

“What part didn’t you understand?”

“All of it.”

I proceeded to try to explain it to her. And she still didn’t understand. After several minutes of this, she said she had a headache and walked away.

So I’ve come up with a brilliant twist. So brilliant, apparently it’s impossible to understand.